Chromate removal from water using red mud and crossflow microfiltration

Red mud was used as an adsorbent for removal of chromate ions from water using crossflow microfiltration. The chromate rejection is a strong function of feed dispersion pH, chromate and red mud concentration ratio, electrolyte concentration, membrane pore size as well as the concentration of co-ions such a sulfate ions used to adjust the dispersion pH. Under certain conditions, especially when pH = 5.2, the chromate rejection reached a maximum of 100% rejection. It was observed that the efficiency of the chromate removal increased with increasing red mud/chromate concentration ratio; however, the steady-state permeate flux decreased with an increasing red mud/chromate ratio. In the presence of chromate (at the same red mud concentration) and electrolyte (at the same chromate and red mud concentrations), permeate flux increased, although the chromate rejections decreased. Furthermore, it was observed that the rejection of chromate decreased with increasing membrane pore size. On the contrary, permeate flux increased with increasing membrane pore size. The method was found to be effective in removing chromate from water.